Understanding Mott-Schottky Measurements under Illumination in Organic Bulk Heterojunction Solar Cells

Abstract

The Mott-Schottky analysis in the dark is a frequently used method to determine the doping concentration of semiconductors from capacitance-voltage measurements, even for such complex systems as polymer:fullerene blends used for organic solar cells. While the analysis of capacitance-voltage measurements in the dark is relatively well established, the analysis of data taken under illumination is currently not fully understood. Here, we present experiments and simulations to show which physical mechanisms affect the Mott-Schottky analysis under illumination. We show that the mobility of the blend has a major influence on the shape of the capacitance-voltage curve and can be obtained from data taken under reverse bias. In addition, we show that the apparent shift of the built-in voltage observed previously can be explained by a shift of the onset of space-charge-limited collection with illumination intensity.

Defect Study and Modelling of SnX3-Based Perovskite Solar Cells with SCAPS-1D

“…It was already reported that the current is significantly lesser than the saturation current at low voltages, but the current was restricted to the saturation current at the contact at high voltages [ 59 ]. The lower value of the built-in potential (Vbi), obtained from the Mott-Schottky plot under illumination, can be ascribed to the capacitance originating from the photogenerated charge carriers that can build up in the low-mobility materials, even at reverse bias [ 60 ]. When doping concentration increases, charge accumulation increases at the interface and the capacitance value will also rise.…”

Extraordinarily long diffusion length in PM6:Y6 organic solar cells

“…18 By conducting the measurements in the dark, where the mobility of the carriers does not affect the device electrostatics, we can establish the depletion region caused by unintentional doping rather than a mobility imbalance. 17,18 The results of the capacitance-voltage experiments in the dark and the Mott-Schottky plots for the 100-nm and 300-nm devices, along with the derivative doping profiles across the active layer width are demonstrated in Fig. 3.…”

“…The measurements were performed in the C p mode. 17 The performance of the devices was tested both prior to and after the C-V measurements with no sign of degradation. Mobility measurements.…”

Adduct-based p-doping of organic semiconductors

“…Mott-Schottky analysis on thick devices has been performed according to ref [3][4][5][6][7] . This analysis is based on the understanding that the depletion width at a semiconductor-metal contact changes with variation in the reverse bias potential.…”